updated contributing.md, added GitHub templates

.github/issue_template.md

@@ -0,0 +1,16 @@
+- bug report? yes/no
+- feature request? yes/no
+- version: ?.?.? <!-- exact release version, for bug reports -->
+
+### Description
+...
+
+### Steps To Reproduce
+... If possible a minimal demo of the problem ...
+
+<!--
+REMEMBER, AN ISSUE IS NOT THE PLACE TO ASK QUESTIONS. We will be happy to help you on Gitter https://gitter.im/nette/nette
+
+A good bug report shouldn't leave others needing to chase you up for more information. Please try to be as detailed as possible in your report.
+Feature requests are welcome. Explain your intentions. It's up to you to make a strong case to convince the project's developers of the merits of this feature.
+-->

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+- bug fix? yes/no   <!-- #issue numbers, if any -->
+- new feature? yes/no
+- BC break? yes/no
+
+<!--
+Describe your changes here to communicate to the maintainers why we should accept this pull request.
+
+Please add new tests to show the fix or feature works.
+
+Thanks for contributing!
+-->